The severity, chronicity, and treatment resistance of depressive disorders occurring in children 6 and older has been established by numerous investigations. Despite the interest in earlier identification and intervention for these children, there is a remarkable paucity of data on depressive syndromes in children younger than 6. This K08 application provides an integrated career development plan and research project to investigate the understudied area of preschool depressive syndromes. The aim of the proposed study is to develop age specific criteria for depressive syndromes in preschool children using a case-control design that compares 200 clinically referred preschool children with depressive symptoms to 100 preschoolers from a community control group with and without these symptoms. This design is well suited to this aim because of the importance of identifying guidelines to distinguish depressive symptom states that are transient and developmentally normative from those that represent clinical syndromes. The identification of depressive symptom states in this age group in a number of high risk studies strongly supports the potential to identify age specific criteria for depressive syndromes in preschool children. Evidence of changes in vagal tone and EEG in high risk infants suggest that biological changes are already occurring at this early stage of development, supporting the rationale for early identification and intervention. The career development plan includes the mentorship of two national leaders, Lee Robins, Ph.D., and Robert Emde, M.D., in the areas of diagnostic classification and early emotional development, and the active on-site consultation of Barbara Geller. M.D., a pioneer in the area of depressive disorders in childhood. Because of promising vagal tone and EEG findings in infants at risk for depression, the applicant will, as part of the career development plan, learn techniques for measuring vagal tone and EEG in preschool subjects in the laboratory of Nathan Fox, Ph.D., piloting these measures in the proposed sample in year III. Group differences between the clinically referred and community samples will be examined and factor analysis will be used to detect symptom clusters. Multiple regressions will test the relationship between symptom clusters and functional impairment, and path analysis will be used to investigate the stability of symptoms over time. The proposed study will provide age specific criteria for depressive syndromes in preschool children, which can serve as the foundation for future investigations of the neurobiology and treatment of depressive syndromes in the preschool period.